Hard on the heels of Microsoft's decision to offer "do not track" functionality in its upcoming Internet Explorer 9 browser comes word that Mozilla is planning a similar move for its Firefox 4.

"Technology that supports something like a 'Do Not Track' button is needed and we will deliver in the first part of next year," Mozilla chief executive Gary Kovacs reportedly told Agence France-Presse while demonstrating Firefox 4 recently at Mozilla headquarters. "The user needs to be in control."

While acknowledging that the issue is a complex one that will require balancing the needs of users and advertisers, "I fundamentally believe that the balance is tipped too far," Kovacs said. "You can't tell me the delivery of a piece of content is going to be that much better if you know everything about my life."

In short, "It's all about moderation," he added.

The PEBKAC Factor

Microsoft's announcemen two weeks ago came soon after the U.S. Federal Trade Commission's proposal that consumers be allowed to subscribe to a "do not track" system similar to the "do not call" lists used to block telemarketers.

Microsoft's new feature is expected in the release candidate version of Internet Explorer 9 that's due early next year. To put the feature to work, users will turn it on and select a list of sites to block.

Of course, like so many software features, how well it works depends largely on how well users understand it and make it work for them. As my PCWorld colleague Tony Bradley recently pointed out, user error could play a significant role.

Problems could exist, in other words, between the keyboard and the chair (PEBKAC).

Opting Out by Default

Over at Mozilla, meanwhile, discussions have actually been going on since May of this year about the possibility of allowing third-party cookies only until a Firefox session is closed. Effectively, that would mean that the user opts out of online tracking by default.

That feature apparently didn't get implemented, but now -- in the wake of the FTC-inspired discussions -- the sentiment has been revived.

It's not yet clear what form Firefox's feature will take or how it will work, and Mozilla didn't get back to me in time for this post. What is clear, however, is that "do not track" capabilities are going to take center stage in the browser arena next year.